<!DOCTYPE html>
<html lang="zh" dir="ltr" class="client-nojs">
<head>
<title>生存期</title>
<meta charset="UTF-8">
<meta name="generator" content="MediaWiki 1.21.2">
<link rel="shortcut icon" href="../../../common/favicon.ico">
<link rel="stylesheet" href="../../../common/ext.css">
<meta name="ResourceLoaderDynamicStyles" content="">
<link rel="stylesheet" href="../../../common/site_modules.css">
<style>a:lang(ar),a:lang(ckb),a:lang(fa),a:lang(kk-arab),a:lang(mzn),a:lang(ps),a:lang(ur){text-decoration:none}#toc{display:none}.editsection{display:none}
/* cache key: mwiki1-mwiki_zh_:resourceloader:filter:minify-css:7:15cea3ec788a65b5187d4018eed543bf */</style>

<script src="../../../common/startup_scripts.js"></script>
<script>if(window.mw){
mw.config.set({"wgCanonicalNamespace":"","wgCanonicalSpecialPageName":false,"wgNamespaceNumber":0,"wgPageName":"c/language/lifetime","wgTitle":"c/language/lifetime","wgCurRevisionId":51272,"wgArticleId":7942,"wgIsArticle":true,"wgAction":"view","wgUserName":null,"wgUserGroups":["*"],"wgCategories":[],"wgBreakFrames":false,"wgPageContentLanguage":"zh","wgSeparatorTransformTable":["",""],"wgDigitTransformTable":["",""],"wgDefaultDateFormat":"zh","wgMonthNames":["","1月","2月","3月","4月","5月","6月","7月","8月","9月","10月","11月","12月"],"wgMonthNamesShort":["","1月","2月","3月","4月","5月","6月","7月","8月","9月","10月","11月","12月"],"wgRelevantPageName":"c/language/lifetime","wgUserVariant":"zh","wgRestrictionEdit":[],"wgRestrictionMove":[]});
}</script><script>if(window.mw){
mw.loader.implement("user.options",function(){mw.user.options.set({"ccmeonemails":0,"cols":80,"date":"default","diffonly":0,"disablemail":0,"disablesuggest":0,"editfont":"default","editondblclick":0,"editsection":0,"editsectiononrightclick":0,"enotifminoredits":0,"enotifrevealaddr":0,"enotifusertalkpages":1,"enotifwatchlistpages":0,"extendwatchlist":0,"externaldiff":0,"externaleditor":0,"fancysig":0,"forceeditsummary":0,"gender":"unknown","hideminor":0,"hidepatrolled":0,"imagesize":2,"justify":0,"math":1,"minordefault":0,"newpageshidepatrolled":0,"nocache":0,"noconvertlink":0,"norollbackdiff":0,"numberheadings":0,"previewonfirst":0,"previewontop":1,"quickbar":5,"rcdays":7,"rclimit":50,"rememberpassword":0,"rows":25,"searchlimit":20,"showhiddencats":0,"showjumplinks":1,"shownumberswatching":1,"showtoc":0,"showtoolbar":1,"skin":"cppreference2","stubthreshold":0,"thumbsize":2,"underline":2,"uselivepreview":0,"usenewrc":0,"watchcreations":0,"watchdefault":0,"watchdeletion":0,
"watchlistdays":3,"watchlisthideanons":0,"watchlisthidebots":0,"watchlisthideliu":0,"watchlisthideminor":0,"watchlisthideown":0,"watchlisthidepatrolled":0,"watchmoves":0,"wllimit":250,"variant":"zh","language":"zh","searchNs0":true,"searchNs1":false,"searchNs2":false,"searchNs3":false,"searchNs4":false,"searchNs5":false,"searchNs6":false,"searchNs7":false,"searchNs8":false,"searchNs9":false,"searchNs10":false,"searchNs11":false,"searchNs12":false,"searchNs13":false,"searchNs14":false,"searchNs15":false,"gadget-MathJax":1,"gadget-ColiruCompiler":1});;},{},{});mw.loader.implement("user.tokens",function(){mw.user.tokens.set({"editToken":"+\\","patrolToken":false,"watchToken":false});;},{},{});
/* cache key: mwiki1-mwiki_zh_:resourceloader:filter:minify-js:7:258d7cd6aa9aa67dee25e01fb6a9e505 */
}</script>
<script>if(window.mw){
mw.loader.load(["mediawiki.page.startup","mediawiki.legacy.wikibits","mediawiki.legacy.ajax"]);
}</script>
<style type="text/css">/*<![CDATA[*/
.source-c {line-height: normal;}
.source-c li, .source-c pre {
	line-height: normal; border: 0px none white;
}
/**
 * GeSHi Dynamically Generated Stylesheet
 * --------------------------------------
 * Dynamically generated stylesheet for c
 * CSS class: source-c, CSS id: 
 * GeSHi (C) 2004 - 2007 Nigel McNie, 2007 - 2008 Benny Baumann
 * (http://qbnz.com/highlighter/ and http://geshi.org/)
 * --------------------------------------
 */
.c.source-c .de1, .c.source-c .de2 {font: normal normal 1em/1.2em monospace; margin:0; padding:0; background:none; vertical-align:top;}
.c.source-c  {font-family:monospace;}
.c.source-c .imp {font-weight: bold; color: red;}
.c.source-c li, .c.source-c .li1 {font-weight: normal; vertical-align:top;}
.c.source-c .ln {width:1px;text-align:right;margin:0;padding:0 2px;vertical-align:top;}
.c.source-c .li2 {font-weight: bold; vertical-align:top;}
.c.source-c .kw1 {color: #0000dd;}
.c.source-c .kw2 {color: #0000ff;}
.c.source-c .kw3 {color: #0000dd;}
.c.source-c .kw4 {color: #0000ff;}
.c.source-c .co1 {color: #909090;}
.c.source-c .co2 {color: #339900;}
.c.source-c .coMULTI {color: #ff0000; font-style: italic;}
.c.source-c .es0 {color: #008000; font-weight: bold;}
.c.source-c .es1 {color: #008000; font-weight: bold;}
.c.source-c .es2 {color: #008000; font-weight: bold;}
.c.source-c .es3 {color: #008000; font-weight: bold;}
.c.source-c .es4 {color: #008000; font-weight: bold;}
.c.source-c .es5 {color: #008000; font-weight: bold;}
.c.source-c .br0 {color: #008000;}
.c.source-c .sy0 {color: #008000;}
.c.source-c .sy1 {color: #000080;}
.c.source-c .sy2 {color: #000040;}
.c.source-c .sy3 {color: #000040;}
.c.source-c .sy4 {color: #008080;}
.c.source-c .st0 {color: #008000;}
.c.source-c .nu0 {color: #000080;}
.c.source-c .nu6 {color:#000080;}
.c.source-c .nu8 {color:#000080;}
.c.source-c .nu12 {color:#000080;}
.c.source-c .nu16 {color:#000080;}
.c.source-c .nu17 {color:#000080;}
.c.source-c .nu18 {color:#000080;}
.c.source-c .nu19 {color:#000080;}
.c.source-c .ln-xtra, .c.source-c li.ln-xtra, .c.source-c div.ln-xtra {background-color: #ffc;}
.c.source-c span.xtra { display:block; }

/*]]>*/
</style><!--[if lt IE 7]><style type="text/css">body{behavior:url("/mwiki/skins/cppreference2/csshover.min.htc")}</style><![endif]--></head>
<body class="mediawiki ltr sitedir-ltr ns-0 ns-subject page-c_language_lifetime skin-cppreference2 action-view cpp-navbar">
        <!-- header -->
        <!-- /header -->
        <!-- content -->
<div id="cpp-content-base">
            <div id="content">
                <a id="top"></a>
                <div id="mw-js-message" style="display:none;"></div>
                                <!-- firstHeading -->
<h1 id="firstHeading" class="firstHeading">生存期</h1>
                <!-- /firstHeading -->
                <!-- bodyContent -->
                <div id="bodyContent">
                                        <!-- tagline -->
                    <div id="siteSub">来自cppreference.com</div>
                    <!-- /tagline -->
                                        <!-- subtitle -->
                    <div id="contentSub"><span class="subpages">&lt; <a href="../../c.html" title="c">c</a>‎ | <a href="../language.html" title="c/language">language</a></span></div>
                    <!-- /subtitle -->
                                                            <!-- bodycontent -->
                    <div id="mw-content-text" lang="zh" dir="ltr" class="mw-content-ltr"><div class="t-navbar" style=""><div class="t-navbar-sep"> </div><div class="t-navbar-head"><a href="../../c.html" title="c"> C</a><div class="t-navbar-menu"><div><div><table class="t-nv-begin" cellpadding="0" style="line-height:1.1em;">
<tr class="t-nv"><td colspan="5"> <a href="../language.html" title="c/language">语言</a> </td></tr>
<tr class="t-nv"><td colspan="5"> <a href="../header.html" title="c/header">头文件</a> </td></tr>
<tr class="t-nv"><td colspan="5"> <a href="../types.html" title="c/types">类型支持</a> </td></tr>
<tr class="t-nv"><td colspan="5"> <a href="../program.html" title="c/program">程序工具</a> </td></tr>
<tr class="t-nv"><td colspan="5"> <a href="../variadic.html" title="c/variadic">变参数函数支持</a> </td></tr>
<tr class="t-nv"><td colspan="5"> <a href="../memory.html" title="c/memory">动态内存管理</a> </td></tr>
<tr class="t-nv"><td colspan="5"> <a href="../error.html" title="c/error">错误处理</a> </td></tr>
<tr class="t-nv"><td colspan="5"> <a href="../chrono.html" title="c/chrono">日期和时间工具</a> </td></tr>
<tr class="t-nv"><td colspan="5"> <a href="../string.html" title="c/string">字符串库</a> </td></tr>
<tr class="t-nv"><td colspan="5"> <a href="../algorithm.html" title="c/algorithm">算法</a> </td></tr>
<tr class="t-nv"><td colspan="5"> <a href="../numeric.html" title="c/numeric">数值</a> </td></tr>
<tr class="t-nv"><td colspan="5"> <a href="../io.html" title="c/io">输入/输出支持</a> </td></tr>
<tr class="t-nv"><td colspan="5"> <a href="../locale.html" title="c/locale">本地化支持</a> </td></tr>
<tr class="t-nv"><td colspan="5"> <a href="../thread.html" title="c/thread">线程支持</a> <span class="t-mark-rev t-since-c11">(C11)</span> </td></tr>
<tr class="t-nv"><td colspan="5"> <a href="../atomic.html" title="c/atomic">原子操作</a> <span class="t-mark-rev t-since-c11">(C11)</span> </td></tr>
<tr class="t-nv"><td colspan="5"> <a href="../experimental.html" title="c/experimental">技术规范</a> </td></tr>
</table></div><div></div></div></div></div><div class="t-navbar-sep"> </div><div class="t-navbar-head"><a href="../language.html" title="c/language">C 语言</a></div><div class="t-navbar-sep"> </div><div class="t-navbar-head"><a href="basic_concepts.html" title="c/language/basic concepts">基本概念</a><div class="t-navbar-menu"><div><div style="display:inline-block">
<div><table class="t-nv-begin" cellpadding="0" style="">
<tr class="t-nv"><td colspan="5"> <a href="../comment.html" title="c/comment">注释</a></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="ascii.html" title="c/language/ascii">ASCII</a></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="escape.html" title="c/language/escape">转义序列</a></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="translation_phases.html" title="c/language/translation phases">翻译阶段</a></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="identifier.html" title="c/language/identifier">标识符</a></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="scope.html" title="c/language/scope">作用域</a></td></tr>
<tr class="t-nv"><td colspan="5"> <strong class="selflink">生存期</strong></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="name_space.html" title="c/language/name space">查找与命名空间</a></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="type.html" title="c/language/types">类型</a></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="object.html" title="c/language/object">对象与对齐</a></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="arithmetic_types.html" title="c/language/arithmetic types">算术类型</a></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="main_function.html" title="c/language/main function"><code>main()</code> 函数</a></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="https://zh.cppreference.com/mwiki/index.php?title=c/language/as_if&amp;action=edit&amp;redlink=1" class="new" title="c/language/as if（页面不存在）">如同规则</a></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="behavior.html" title="c/language/behavior">未定义行为</a></td></tr>
<tr class="t-nv"><td colspan="5"> <a href="memory_model.html" title="c/language/memory model">内存模型与数据竞争</a></td></tr>
</table></div>
</div><div></div></div></div></div><div class="t-navbar-sep"> </div></div>
<p>C 中每个<a href="object.html" title="c/language/object">对象</a>存在、拥有常地址、保有其最近一次存储值（除非其值不确定）<span class="t-rev-inl t-since-c99"><span>，对于 VLA 还有保有其大小</span> <span><span class="t-mark-rev t-since-c99">(C99 起)</span></span></span>的程序执行部分，被称作该对象的<i>生存期</i>。
</p><p>对于声明有自动、静态及线程存储期的对象，生存期等于其<a href="storage_duration.html" title="c/language/storage duration">存储期</a>（注意非 VLA 和 VLA 自动存储期的区别）。
</p><p>对于拥有分配存储期的对象，其生存期始于分配函数的返回（包含从 <span class="t-lc"><a href="../memory/realloc.html" title="c/memory/realloc">realloc</a></span> 返回），终于 <span class="t-lc"><a href="../memory/realloc.html" title="c/memory/realloc">realloc</a></span> 或解分配函数的调用。注意因为分配的对象没有<a href="object.html" title="c/language/object">声明类型</a>，首次访问该对象所用的左值表达式类型会成为其<a href="object.html#.E6.9C.89.E6.95.88.E7.B1.BB.E5.9E.8B" title="c/language/object">有效类型</a>。
</p><p>在生存期外访问对象是未定义行为。
</p>
<div dir="ltr" class="mw-geshi" style="text-align: left;"><div class="c source-c"><pre class="de1"><span class="kw4">int</span><span class="sy2">*</span> foo<span class="br0">(</span><span class="kw4">void</span><span class="br0">)</span> <span class="br0">{</span>
    <span class="kw4">int</span> a <span class="sy1">=</span> <span class="nu0">17</span><span class="sy4">;</span> <span class="co1">// a拥有自动存储期</span>
    <span class="kw1">return</span> <span class="sy3">&amp;</span>a<span class="sy4">;</span>
<span class="br0">}</span>  <span class="co1">// a的生存期结束</span>
<span class="kw4">int</span> main<span class="br0">(</span><span class="kw4">void</span><span class="br0">)</span> <span class="br0">{</span>
    <span class="kw4">int</span><span class="sy2">*</span> p <span class="sy1">=</span> foo<span class="br0">(</span><span class="br0">)</span><span class="sy4">;</span> <span class="co1">// p 指向生存期结束后的对象（“悬垂指针”）</span>
    <span class="kw4">int</span> n <span class="sy1">=</span> <span class="sy2">*</span>p<span class="sy4">;</span> <span class="co1">// 未定义行为</span>
<span class="br0">}</span></pre></div></div>
<p>指向生存期结束的对象（或该对象后一位置）的指针拥有不确定值。
</p>
<h3><span class="mw-headline" id=".E4.B8.B4.E6.97.B6.E7.94.9F.E5.AD.98.E6.9C.9F">临时生存期</span></h3>
<p><a href="value_category.html" title="c/language/value category">非左值表达式</a>所指代的拥有数组成员的结构体和联合体对象（直接为其成员或为嵌套的结构体/联合体成员）拥有<i>临时生存期</i>。临时生存期始于求值指代该对象的表达式，终于<span class="t-rev-inl t-until-c11"><span>下一个<a href="eval_order.html" title="c/language/eval order">序列点</a></span> <span><span class="t-mark-rev t-until-c11">(C11 前)</span></span></span><span class="t-rev-inl t-since-c11"><span>包含它的完整表达式或完整声明器结束</span> <span><span class="t-mark-rev t-since-c11">(C11 起)</span></span></span>。
</p><p>任何修改临时生存期对象的尝试会导致未定义行为。
</p>
<div dir="ltr" class="mw-geshi" style="text-align: left;"><div class="c source-c"><pre class="de1"><span class="kw1">struct</span> T <span class="br0">{</span> <span class="kw4">double</span> a<span class="br0">[</span><span class="nu0">4</span><span class="br0">]</span><span class="sy4">;</span> <span class="br0">}</span><span class="sy4">;</span>
<span class="kw1">struct</span> T f<span class="br0">(</span><span class="kw4">void</span><span class="br0">)</span> <span class="br0">{</span> <span class="kw1">return</span> <span class="br0">(</span><span class="kw1">struct</span> T<span class="br0">)</span><span class="br0">{</span><span class="nu16">3.15</span><span class="br0">}</span><span class="sy4">;</span> <span class="br0">}</span>
<span class="kw4">double</span> g1<span class="br0">(</span><span class="kw4">double</span><span class="sy2">*</span> x<span class="br0">)</span> <span class="br0">{</span> <span class="kw1">return</span> <span class="sy2">*</span>x<span class="sy4">;</span> <span class="br0">}</span>
<span class="kw4">void</span> g2<span class="br0">(</span><span class="kw4">double</span><span class="sy2">*</span> x<span class="br0">)</span> <span class="br0">{</span> <span class="sy2">*</span>x <span class="sy1">=</span> <span class="nu16">1.0</span><span class="sy4">;</span> <span class="br0">}</span>
<span class="kw4">int</span> main<span class="br0">(</span><span class="kw4">void</span><span class="br0">)</span>
<span class="br0">{</span>
    <span class="kw4">double</span> d <span class="sy1">=</span> g1<span class="br0">(</span>f<span class="br0">(</span><span class="br0">)</span>.<span class="me1">a</span><span class="br0">)</span><span class="sy4">;</span> <span class="co1">// C99 ： UB 访问生存期结束于 g1 开序列点的 a[0]</span>
                          <span class="co1">// C11 ： OK ， d 为 3.15</span>
    g2<span class="br0">(</span>f<span class="br0">(</span><span class="br0">)</span>.<span class="me1">a</span><span class="br0">)</span><span class="sy4">;</span> <span class="co1">// C99 ： UB 修改生存期结束于序列点的 a[0]</span>
               <span class="co1">// C11 ： UB 试图修改临时对象</span>
<span class="br0">}</span></pre></div></div>
<h3><span class="mw-headline" id=".E5.BC.95.E7.94.A8">引用</span></h3>
<div class="t-ref-std-11">
<ul><li> C11 standard (ISO/IEC 9899:2011): 
</li></ul>
<dl><dd><ul><li> 6.2.4 Storage durations of objects (p: 38-39)
</li></ul>
</dd></dl>
<div class="t-ref-std-c99">
<ul><li> C99 standard (ISO/IEC 9899:1999): 
</li></ul>
<dl><dd><ul><li> 6.2.4 Storage durations of objects (p: 32)
</li></ul>
</dd></dl>
<div class="t-ref-std-c89">
<ul><li> C89/C90 standard (ISO/IEC 9899:1990): 
</li></ul>
<dl><dd><ul><li> 3.1.2.4 Storage durations of objects 
</li></ul>
</dd></dl>
</div>
<h3><span class="mw-headline" id=".E5.8F.82.E9.98.85">参阅</span></h3>
<table class="t-dsc-begin">

</table></div>
</div>

<!-- 
NewPP limit report
Preprocessor visited node count: 900/1000000
Preprocessor generated node count: 3468/1000000
Post‐expand include size: 24898/2097152 bytes
Template argument size: 3215/2097152 bytes
Highest expansion depth: 13/40
Expensive parser function count: 0/100
-->

<!-- Saved in parser cache with key mwiki1-mwiki_zh_:pcache:idhash:7942-0!*!0!!*!*!zh!* and timestamp 20200216200642 -->
</div>                    <!-- /bodycontent -->
                                        <!-- printfooter -->
                    <div class="printfooter">
                    来自“<a href="https://zh.cppreference.com/mwiki/index.php?title=c/language/lifetime&amp;oldid=51272">https://zh.cppreference.com/mwiki/index.php?title=c/language/lifetime&amp;oldid=51272</a>”                    </div>
                    <!-- /printfooter -->
                                                            <!-- catlinks -->
                    <!-- /catlinks -->
                                                            <div class="visualClear"></div>
                    <!-- debughtml -->
                                        <!-- /debughtml -->
                </div>
                <!-- /bodyContent -->
            </div>
        </div>
        <!-- /content -->
        <!-- footer -->
        <div id="cpp-footer-base" class="noprint">
            <div id="footer">
                        <div id="cpp-navigation">
            <h5>导航</h5>
            <ul><li><a href="https://zh.cppreference.com/w/c/language/lifetime">Online version</a></li><li>Offline version retrieved 2020-03-14 18:00.</li></ul></div>
                        <ul id="footer-info">
                                    <li id="footer-info-lastmod"> 本页面最后修改于2017年11月29日 (星期三) 09:01。</li>
                                    <li id="footer-info-viewcount">此页面已被浏览过2,634次。</li>
                            </ul>
                    </div>
        </div>
        <!-- /footer -->
        <script>if(window.mw){
mw.loader.state({"site":"loading","user":"missing","user.groups":"ready"});
}</script>
<script src="../../../common/skin_scripts.js"></script>
<script>if(window.mw){
mw.loader.load(["mediawiki.action.view.postEdit","mediawiki.user","mediawiki.page.ready","mediawiki.searchSuggest","mediawiki.hidpi","ext.gadget.MathJax","ext.gadget.ColiruCompiler"], null, true);
}</script>
<script src="../../../common/site_scripts.js"></script>
<script type="text/javascript">
var _gaq = _gaq || [];
_gaq.push(['_setAccount', 'UA-2828341-1']);
_gaq.push(['_setDomainName', 'cppreference.com']);
_gaq.push(['_trackPageview']);
</script><!-- Served in 0.352 secs. -->
	</body>
<!-- Cached 20200216200642 -->
</html>